Electric transmitting and receiving apparatus



6 OO A, 5 7 uw l N .N Sh\ SY S Filed July 2. 1931 l I C A A THOMAS ELECTRIC TRANSMITTING AND RECEIVING APPARATUS ci. 2, 1934. A A, A THOMAS 1,975,486

ELECTRIC TRANSMITTIG AND RECEIVING APPARATUS Filed July 2. 1931 4 Sheets-Sheet 2 INVENTOR Filed July 2. 1951 A A THOMAS ELECTRIC TANSMITTING AND RECEIVING APEARATUS oct. 2,'1934.

'@cc'., 2, 193% A. A. 'THOMAS ELECTRIC TRANSMITTNG- AND RECEIVING APPARATUS Filed July 2, 1931 4 Sheets-Sheet INVENTOR yPatented Oct. 2, 1934 PATENT oFFic ELEC'ERHC TRANSIWI'ETING RECEEVHNG APPARATUS Adolph A. Thomas, New York, N. Y.

Application `lluly 2, 1931, Serial No. 548,233

32 Claims.

This invention relates to electric transmitting and receiving systems for controlling the operal tion of suitable devices having a plurality of selectively operable members. At the present d time my invention finds special utility in operating typewriters, type-setting machines and the like, by means of radio impulses', although it is not limited to that particular field. In explaining the practical advantages of my invention, I shall describe, by way of example, a system in which a manually operated typewriter (or other printer) at the transmitting end controls one or more typewriters at the receiving end to print an exact duplicate of the message typed on the transmitting machine.

The characteristic feature of novelty in my improved remote control system comprises a plurality of selective circuits in the transmitting apparatus for generating sets of impulses of different frequencies which are impressed upon the carrier 'wave to modify the same. The receiving apparatus has a corresponding plurality of tuned circuits, each of which is energized by only one set of transmitted frequencies. Thus, when the operator of the transmitting typewriter strikes a certain' key, one of the selective circuits is closed to impress electric impulses of a certain frequency on the carrier wave, and these impulses energize only one of the tuned receiving circuits to actuate the corresponding key in the receiving typewriter. In other words, Whatever operation is manually performed on the transmitting machine is automatically repeated by the receiving machine, and I would emphasize the fact that this remote control of one machine by the other is accomplished without the use of synchronizing mechanism (which is elaborate and expensive) and without resort to the idea of a variously timed succession of impulses heretofore employed in operating telegraph tape printers. The transmitting and receiving apparatus of my radio-dynamic system are comparatively simple and compact, without any parts requiring critical ladjustment or easy to get out of order, and the absence of all timing mechanism makes the operation of the system reliable to the point of certainty. The sending and receiving stations of my system may be operatively connected by 'wire or by radio control.

The novel features and practical advantages of my invention will be understood from a description of the accompanying drawings, in which- Fig. 1 is a diagrammatic representation of my transmitting and receiving system as applied to the distant control of a typewriter or other machine having a plurality of selectively operable par s;

Fig. 2 illustrates diagrammatically an electric motor adapted to operate a set of circuit breakers to generate electric impulses of predetermined frequencies in a corresponding plurality of selector circuits;

Fig. 3 is a mechanical detail of Fig. 2, showing a convenient way of mounting and arranging the circuit-.breaker disks on the motor shaft;

Fig. d'shows an operating key and associated switch in the transmitting typewriter;

Fig. 5 is a fragmentary view of a key and its operating solenoid in the receiving typewriter;

Fig. 6 is a fragmentary end view of the receiving typewriter to show how the platen is rotated by a solenoid;

Fig. l represents a top view of the hand-shifted platen carriage in the transmitting machine;

Fig. 8 is a top view of the motor-operated platen carriage in the receiving machine;

Fig. 9 is a detached perspective of the automatic tripping device operated by the platen carriage of the receiving machine;

Fig. 10- illustrates an enlarged view of the clutch-controlled connections between the motor shaft and the pinion that returns the platen carriage of the receiving machine to starting position;

Fig. 11 shows the circuit connections for the clutch coil of Fig. 10;

Fig. 12 is a diagrammatic showing of a suitable form of relay switch associated with the receiving machine;

Fig. 13 shows the two switches operated by the down and up movements of the shift key in the transmitting typewriter;

Fig. 14 is an enlarged View of the cam shown in Fig. 13;

Fig. 15 shows an enlarged section on line 15-15 of Fig. 13;

Fig. 16 representsafsection on line 16-16 of Fig. 15; and

Fig. 17 shows the electromagnetic mechanism 10o associated with the shift key of the receiving typewriter and controlled by the switches of Fig. 13.

In the diagrammatic illustration of Fig. 1 I have indicated only so much of radio transmit- 105 ting and receiving systems as is necessary for a description of Amy invention. Since the details of broadcasting and receiving apparatus are well understood, they require no explanation here.

In the present instance, the apparatus at the 11g plate transmitting station includes a pair of vacuum tubes 10 and 12 suitably connected in amplifying relation for transmitting electric oscillations from the input transformer 13 to the broadcasting antenna. 14. The transformer 13 comprises a main primary coil 15, an auxiliary primary coil 16, and a secondary coil 17 in inductive relation to both primary coils. The main primary coil 15 is connected to a suitable source of electric oscillations of a certain allotted frequency which constitute the carrier wave of the station. The auxiliary primary coil 16 is adapted to be connected in any one of a plurality of modulating circuits which oscillate at different predetermined frequencies, as I shall presently explain, and the electric impulses in coil 16 are impressed upon (and thus modify) the permanent frequency of the carrier wave. In other words, the character of the oscillations induced in the secondary coil 17 is due to the `combined effect of the impulses in primary coils l5 and 16. The oscillations in coil 15 are preferably of higher frequency than those of the modulating circuits in which coil.16 is connected. The oscillations in coil 17 are amplied by thetubes 10 and 12 to the required degree before they -reach the sending aerial 14. It

lwill not be necessary to describe the circuit connections between coil 17 and aerial 14, because they are obvious from the drawings and are not, in themselves, part of this invention, for any suitable broadcasting equipment may be used.

The auxiliary primary coil 16, which may ,be called the modulating coil, is connected in the circuit of battery 18 or other source of substantially constant direct current. One side of coil 16 is connected by a wire 19 to a common conductor 20, which is connected to the return main 2l of the battery through a plurality of modulating circuits 22 arranged in parallel or otherwise for individual control. Only convenient number of modulating circuits is indicated in Fig. 1, and the individual circuits are identified by the sumx letters a to 7c. If We assume that my invention is used for operating a. typewriter, type setter or other printer by radio, each key and other hand-operable member of the transmitting machine controls one of the branch circuits 22 for sending impulses of a predetermined frequency through the modulating coil 16.

Each modulating circuit 22 includes a device 23 for generating electric impulses of a certain frequency, and for distinction I have indicated the different devices by the suffix letters a to k. In Fig. 1, the frequency generators 23 are indicated diagrammatically by a rectangular outline, and in Figs. 2-3 I have shown them in the form of conducting disks fixed side by side on the driving shaft 24 of a small electric motor 25. If necessary, spacing Washers 26 may be interposed to separate the disksof which only a few have been shown for convenience, and I- have used sufx letters to distinguish the individual disks. It will be understoodl .that in Fig. 3 the disks 23 are arranged face-Wise for clearness, theactual way of mounting being shown in' Fig. 3. These disks may be punched from a sheet of hard brass or other good conducting metal, and are preferably mounted on both ends of motor shaft 24 for better mechanical balance. Each disk 23 has one or more teeth 26 arranged to engage an associated contact 27, which may be a spring arm, and all these contact arms may be mounted on la single insulated bar arranged parallel with the motor shaft. As this shaft rotates, each disk 23 engages the adjacent contact 27 a certain number of times in one revolution, depending upon the number of teeth on the disk. Ilie five disks 23 shown in Fig. 2 have teeth from oneto five respectively, and it may be assumed that the teeth on the other disks progressively increase in the same ratio. The contacts 27 are connected in the modulating circuits 22, and the metal disks 23 are grounded to the driving shaft 24 which carries an extra diskfgr ringl 28 permanently connected to the return main 21 by a collector brush 29 or the like.

Each modulating circuit 22 has a normally open switch in series with the associated contact 27, each switch comprising a movable arm 30 and contact 31. The vswitch arms 30 are closed by the type keys and other hand-operable members of the transmitting typewriter. In the broad aspect of my invention, the construction and arrangement of switches 30-31 are immaterial, it being only necessary that each hand-operable member of the machine shall control an associated switch. Thus, in Fig. 4 I have show n a type key 32 provided with a projection 33 which strikes the adjacent switch arm 30 and closes it against the contact 31 when the key is pushed down. The members 30-31 may be spring blades adapted to be closed slightly before the key 32 reaches the end of its printing movement and thus remain closed for an appreciable period before the pressed key returns to normal position. rIhe switch members 30-31 for each row of keys may be lmounted on an insulating bar 34 arranged cross-wise of the machine.

Fig. 7 shows a normally open switch 30-31 attached to the platen carriage 35 of the transmitting typewriter, which may be of any standard make. In this instance, the machine has a pivoted nger piece 36 for rotating the platen 37 by the usual pawl and ratchet connection, and also for sliding the carriage 35 back to initial position. When the operator inserts his finger in the hooked end 36' of lever SFS/and swings the latter to the right, the associated switch 30-31 is closed and remains closed during the return movement of the carriage. This comparatively long closing interval of switch 30-31 gives the electromagnetic mechanism in the remote receiving typewriter ample time to rotate the platen and shift the carriage to starting position, as will later become clear. Upon release of lever 36, the spring blades 30-31 automatically open. In Fig. 1, the switch arm actuated by lever 36 is marked 30k to distinguish it from the corresponding switch arms 30 actuated by the keys.

Returning tc Fig. l, the principle of operation of the transmitting apparatus will now be understood. We shall assume that the motor 25 is running at a predetermined constant speedany one of those circuits is in condition for in-v stant use. When the operator strikes a key, the associated switch arm 30 is closed and the circuit 22 of that arm is traversed by electric'impulses of a certain frequency. In other words, the operation of each key (and this includes the platen 36, the usual spacing bar and all other lill@ hand-actuated elements of the machine) sends relectric impulses of a diierent frequency through waves sent out by the transmitting aerial 14 are picked up by the aerial 37 of radio receiver 38, which is supposed to be tuned to the broadcasting frequency of the station.` Any practical construction .of radio receiver may be used, and since such devices are well known I need not go into the details thereof. The output coil 39 of receiver 38 is inductively (or otherwise) connected with a coil 40 which constitutes the source of power for a plurality of tuned parallel circuits 4l. These circuits are dilerentiated by the suffix letters a to 7c to indicate their relation to the corresponding impulse circuits'22a-22Ic in the transmitting station, it being understood that Fig. 1 does not show all the circuits 22 and 41 that may be necessary in any particular form of transmitting and receiving apparatus. Each tuned circuit 41 contains a coil 42 and an electric tuning device 43 which permits only impulses of a certain frequency to pass through the circuit and energize the associatedcoil. The

, tuning devices 43 may be condensers of proper ing typewriter.

capacity, or choke coils and condensers so connected as to render each circuit 41 receptive only to electric oscillations of predetermined frequency. In actual practice the tuning devices 43 may be structurally identical but indi- .vidually adjustable as to capacity and inductance,

so that each circuit may be resonant to its allotted frequency. This will be clear to electrical experts without further explanation.

The coils 42 control each a movable switch arm v44 adapted to engage a contact 45 when the coil is energized. One way of accomplishing, this operation is to mount each coil 42 on a magnet core 46 (see Fig. 12) and make the switch arm 44 a movable armature bar pivoted to the core. A spring 47 normally holds the arm 44 in open position against a Xed stop 48. It is thus seen that each coil 42 is" part of an alternating current relay adapted to hold the arm 44 against contact 45 when the coil is energized by the electric impulses passing through the associated tuned circuit. Any other practical arrangement may be used for closing the normally open switches 44-45 upon energization of coils 42. The switches 44-45 are connected in a plurality of parallel circuits 49 arranged between the main conductors 50 and 51 of a battery 52 Lor other source of current. Each branch circuit 49 contains an operating coil 53 adapted to actuate a type bar or other movable member of the receiva to k to indicate that they correspond to the similarly marked impulse circuits 22 in the transmitting apparatus.' Any practical connections may be used for causing operation of the type bars and platen in the receiving macine by the energizing of coils 53. By way' of example, I have In Fig. 1 the different coils'53 lare individually identified by the suffix letters shown in Fig. 5 a key lever 54 which carries a magnetic core or plunger 55 arranged to be pulled down into coil 53 when the latter is energized. It is assumed that the lever 54 operates a type bar or other element of the `receiving typewriter.

The operation of the receiving apparatuswill be understood from the preceding description, but for convenience I shall summarize it in a few sentences. Let us suppose that the actuation of the E key in the transmitting machine closes the branch circuit 22e. and sends impulses of a certain frequency (say 500) through the modulating coil 16. This means that the output coil 40 in the receiving apparatus will be traversed by oscillations of the same frequency, which will energize (let us say) the tuned circuit 41e, so that the associated coil 42 will 'close the switch arm 44e and thereby energize the operating coil 53e. This coil is connected to the E key of the printing machine, which will therefore print the letter E in either capital or small type, according to the operation of the transmitting machine. In the same way each letter or mark printed on the transmitting machine is reproduced on the receiving machine. It is understood that in operating the transmitting typewriter only one key is actuated at a, time, for only one modulating frequency can effectively pass through coil 16 at any instant'. The sending machine can be operated as fast as an ordinary typewriter, so that the transmission of printed matter islvery rapid.

If the printing machines in the transmitting and receiving stations are typewriters 'with the usual shiftable platen carriage, I provide means for automatically duplicating the platen opera-` tions of`the sending machine in thereceiving machine. receiving typewriter has a slidable carriage 56 in which a rotary platen cylinder 57 is mounted by means of a shaft 58. One end of this shaft rcarries a ratchet 59 and a pair of arms 60--61 -to hold the end of pawl 62 against the ratchet Referring to Figs. 6, 8, 9 and 10, thev teeth. The arm 61 is normally held by a spring 62 in raised position againsta fixed stop 64. A magnetic core or plunger 65 is connected to arm 61 and operatedby coil 53k, which is rigidly mounted on a U-shapedabracket .66 attached to which energizes coil 53k to operate the bellcrank 60-4-61 and thereby rotate the platen 57 of the receiving machine to the next printing position. The downward movement of lever 61 is arrested by a fixed stop 68, so that the platen is rotated through a definite arc to space the lines of type a certain distance.y When the actuated lever 61 is released, the spring 63 instantly pulls it up f against the stop 64, While the pawl 62 rides idly over the ratchet wheel 59. Only one kind of line spacing is necessary, and it is therefore assumed-that the transmitting machine operates slidable movement.

at a predetermined line spacing which is not changed as in. the ordinary commercial typewriters.

The platen carriage 56 of the receiving typewriter is shifted to starting position by a small electric motor 69 (see Fig. 8), which operates a pinion '70 arranged in mesh with a rack bar 7l on the carriage. The circuitl of motor 69 is controlled by a switch 72-73 mounted on bracket 66 (see Fig. 6). If this bracket is of insulating material, no separate insulation is necessary for the switch members '72--73, which may conveniently be in the form of spring blades normally held apart by inherent tension. The spring arm '72 is in the path of a projection 74 on lever 61, whereby the downward movement of the lever closes the arm 72 against contact 73. This energizes the electric motor 69 to shift the carriage 56 quickly to starting position. Since the motor rotates very fast, it takes only a second or so to return the carriage. It is advisable to assure a sufficient closing interval for switch 72-73 independently of the time during which the platen coil 53k is energized, and for this purpose I lock the lever 61 in circuit-closing position by means of a pivoted latch 75 until the carriage has reached the end of its return movement.

Referring to Fig. 6, the latch 75 is a bellcrank` pivot/ed on stud '76 projecting from bracket 66. A contracting coil spring 77 normally holds the rear arm 75' of latch 75 against a fixed stop 78. The lever 61 is provided at its free end with a bevelled-extension 61 adapted to be engaged by the hook 75a of latch 75 just as (or slightly before) the lever reaches the limit of its downward travel. The lever 6l is thus locked in circuitclosing position, as indicated by the dotted outline 61a., and the circuit of motor 69 remains closed even when'coil 53k is de-energized. The latch 75 is automatically moved to releasing position by means of a cam plate 79 mounted on the xed frame 80 of the machine in the path of the arm 75. The fixed cam plate 79 may be an integral end piece of a flat bar 81 and the lower edge 79 of the plate is arranged to be engaged by the free end of latch arm 75'. As shown in Fig. 9, the edge 79 of the cam plate is so inclined that the latch is rocked clockwise away from the4 locked end of lever 61 as the platen carriage approaches the completion of its return movement. The cam edge 79 is so shaped that the latch hook 75a disengages the end 6l of lever 61 just as the v carriage 56 reaches its initial position. When that happens, the quick return of lever 6l by spring 63 opens the switch arm 72 and the motor 69 stops. A suitable slip clutch may be interposed between the motor and pinion 70 to prevent overthrow of the motor shaft when the platen carriage suddenly stops.

When the platen-shifting motor 69 is started from rest position, it takes a certain interval of time (very small, to be sure, but still appreciable) to bring it up to full speed. This lost interval or delayed action of the motor may 'not normally disconnected from the platen-driving pinion 70. When the switch 72--73 is closed, the running motor is automatically clutched vin. A suitable arrangement for accomplishing -this operation is shown in Fig. 10, where the motor shaft 82 has a toothed clutch ring 83 keyed thereon for The pinion 70 is rotatably mounted on a counter -shaft 84 supported in a bearing 85 in alignment with motor shaft 82 and carrying a toothed clutch member 86, which is locked to the counter-shaft by a key 87 or otherwise. The shaft 84 also carries a pair of friction clutch disks 88 and 89, the first disk being slidably keyed to the shaft and the other being rotatableA thereon. An expanding coil spring 90 constantly holds the disk 88 in frictional driving contact with disk 89, which is connected to (or part of) the pinion 70. The'motor 69 -and shaft bearing 85 may besupported on a shelf or bracket 91 attached to the frame 80 of the machine in any practical way. A bell-crank 92 is pivoted on a stud 93', which may be conveniently mounted on the motor bracket 91. The arm 92 of this bell-crank terminates in a yoke arranged to engage at its free ends in a circular groove 83' of the slidable clutch ring 83. A contracting coil spring 9d normally holds the bell-crank 92 against a fixed stop 95, so that the clutch ring 83 is out of engagement with clutch member 86. Therefore, the shaft 84 and pinion 70 are normally disconnected from the motor shaft 82 and are free to move with the platen carriage 56. during the step-by-step operation of the latter from right to left.

The bell-crank 92 is actuated by a solenoid comprising a coil 96 and a magnetic core or plunger 97 which is suitably connected to one arm of the bell-crank. When the coil 96 is energized, the bell-crank 92 is rocked in a direction to shift the clutch ring 83 into driving engagement with the adjacent clutch member 86, whereby the shafts 82 and 84 arecoupled together and move the platen carriage 56 toward the right to starting position. The frictional clutch 88-89 allows rotation of the motor shaft after the carriage has reached the end of its return movement to prevent overstrain of the moving parts. If the clutch members 83 and 86 are of the slip type, the additional clutch 88-89 may be omitted. The clutch coil 96 is connected in series with switch 72--73, but the motor 69 is connected in the circuit of batteryk 52 for continuous operation when the circuit is closed by the main starting switch of the receiving apparatus. The energizing of platen coil 53k is almost instantly followed by the energizing of clutch coil 96 and it takes only a moment for the running motor 69 to shift the platen carriage 56 to starting position. The proper speed of the motor is easily determined by experiment. It should be noted that the circuit of the platenshifting motor69 is local, like the branch circuits 49 of batteryv 52, as will be clear from Figs. l and 1l. Just as the lever 36 in the transmitting machine performs the double function of rotating the platen 37 and shifting the carriage 35 back to starting position, so does the energizing of coil 53k by the closing of switch arm 30k: perform the double function of rotating the platen 57 and causing the motor 69 to return the carriage 56 to initial position.

If the typewriters used in my radio-dynamic system have upper and lower case type, there is a so-called shift key for veither raising the platen or lowering the support of the type bars when it is desired to print from the upper case. This shift key may be automatically locked in depressed position (as when the operator wants to print all capitals) and is then released by means of another key, or it is held down momentarily while the type key is operated. In either event it is necessary to actuate two keys simultaneously; or rather, two keys are held down at the same time, even if only for a moment. Now, as I have already icc right as viewed in Fig. 13).

remarked, it is essential that only one of the modulating impulse circuits 22 in the sending station be closed at one time, and so I provide novel switch means operated by the shift key of the transmitting machine to control the operation of the shift key in the receiving machine. l

Referring to Figs. 13-16, the shift key 98 of the transmitting machine is connected either to the platen carriage for raising the same or to the common support of the yhinged type bars for lowering the latter relatively to the platen cylinder. It will not be necessary to show or describe these connections, because they have been known for a long time in commercial typewriters. The down and up movements of shift key 98 control two different modulating circuits 22 and these circuits are automatically opened before the key is at the end of either movement. Thisnovel idea may be mechanically embodied in various ways, and by way of example I have shown a pair of switches 99-100 and 101- 102 controlled by a pin or roller 103 which is carried by the shift key 98 and is guided by a cam groove 104 in a fixed plate or block 105. The pin or roller 103 is attached to an arm 106 pivoted at 107 to the shift key 98, and a contracting coil spring 108 always tends to pull the arm rearwardly (that is, to the The shift key 98,

like the other keys of the machine, is normally held in raised position, as by a spring 109 or otherwise.

As best shown in Fig. 14, the cam groove 104 is triangular, comprising a pair of diverging tracks l04a and 104b connected by a transverse track 104C. The upper end of track 1041) is normally closed by a swinging gate 110 which is xed on a rotary shaft 112 mounted in the hub 105 of cam plate 105. A cross-pin 112 on shaft 112 moves in a radial slot 105a of hub 105 for limiting the swing of gate 110. A weak spring 113 coiled about hub 105 normally holds the gate closed, this spring being connected at its ends I to plate 105 and shaft 112. In the normal position of shift key4 98, the pin 103 lies in the upper recess or apex 115 of cam groove 104, just above the closed gate 110, which forms in effect a part of track 104a. Therefore, when the key 98 is pushed downthe pin 103 is constrained to follow track 104a; and when the key is at theend of its movement, the pin will be opposite the cross track 104e, as indicated by the dotted circle 103a. The cross-track 104e being slightly wider than pin 103, the latter is not jammed against a wall of the groove, but'is free to be swung by spring 108 to the otherend of the cross-track, as marked by the dotted circle 103D. During the return or upward movement of shift key 98, the pin 103 travels up the track 104b and moves the hinged gate 110 aside to enter the recess 115. When the pin 103 disengages the opened gate 110, the latter is instantly snapped shut by spring 113. It is thus clear that the pin 103 is always forced to travel down the cam track 104a during the downward movement of shift key 98, and up the cam track 104b when the key returns.

Let us now see what happens to the switches 99.100 and 101-102 during the down and up movements of shift key. 98.v The switch'members 99 and 101 are preferably spring arms held normally by inherent tension away from their respective contacts 100 and 102. The four switch elements 99 to 102 are conveniently mounted on cam plate 105, which may be of insulating material to obviate separatev insulation of the switch elements. Each spring arm 99 and 101 is formed with a hump 99 and 101 respectively, and these humps normally project over the cam tracks 104a and 104b into the path of pin 103. Consequently, when the shift key 98 is depressed, the pin 103 moves the switch arm 99 againstcontact 100; and during the return of the key, the other switch arm 101 is actuated by the pin against contact 102. Fig. 14 shows the descending pin 103 in position 103 where it presses the spring arm 99 against contact 100, and the hump 99' is so shaped that this closing interval is of sufficient duration. This also applies to the shape of hump 101 on switch arm 101. It should be noted that the closed switch arms 99 and 101 are again opened before the key 98 reaches the end of each movement. Now, in the operation of the machine, the shift key is always pushed down completely before the next type key is depressed, so that the switch arm 99 is sure to be open before the closing of a modulating circuit 22 by an actuated type key. Also, the opening of the modulating circuit by the released typekey takes place before the closing of switch arm 101 during the return of shift key 98. Consequently, only one modulating circuit 22 is closed when the shift key 98 is held down during the operation of a type key.

In Fig. 17 the shift key 116 of the receiving machine operates suitable connections either for raising the platen carriage or lowering the type support of the machine, as will be understood without further explanation. A solenoid, comprising a fixed coil 117 and a magnetic plunger 118 connected to key 116 by a' link 119, is arranged to pull down the key when the coil is energized. A suitable latch device automatically locks the shift key 116 i'n depressed position, and this device is here shown as a ,swinging catch bar 120 carried by the key and a bell-crank latch 121 pivoted at 122 to a fixed part of the typewriter frame. A spring '123 normally holds the catch-bar 120 against a lug 124 on the key, and a. second spring 125 normally holds the latch 121 against a fixed stop 126, so that the nose 121 of the latch lies normally in the path of the hookshaped end 120 of catch-bar 120. The cooperating ends 120-121 are properly bevelle'd so as to snap into locking engagement just before the key 116 reaches the limit of its downward level. The bell-crank 121 is rocked clockwise to releasingposition by a solenoid comprising a fixed coil 127 and a magnetic plunger 128 attached to the bell-crank. A xed stop 129 limits the movement of bell-crank 121 to a point where the locked ends 120'-121 disengage. When the coil 127 is deenergized, the spring 125 quickly rocks the bellcrank 121 to normal position.

The circuit connections for the electric devices associated with the two shift keys 98 and 116 are such that the closing of switch 99-100 causes energizing of coil 117, and the closing of switch 101-102 energizes the releasing coil 127. In other words, the two switches 99-100 and 101-102 close two modulating circuits 22 of certain frequencies, and two of the tuned receiving circuits 41 correspond to those frequencies. For example, if we suppose that the two shift-key switches 99-100 and 101--102 close the modulating circuits 22j and 22g respectively, the down.- ward movement of shift key 98 will activate the tuned receiving circuit 41f and the return of the key will activate the tuned circuit 41g. This means that coil 53f of Fig. 1 corresponds to coil 117 of Fig. 17 and -is energized to pull down the shift key 116 of the receiving machine. Likewise, in the example given, the releasing coil 127 150 of Fig. 17 corresponds to coil 53g of Fig. 1 and is energized to release the locked shift key 116 when the transmitting shift key 98 returns to normal position. Y f

It will bel clear from the foregoing description that I have provided comparatively simple means for operating aprinting machine and the like by radio broadcast; A single transmitting machine may simultaneously operate any number of receiving machines located in different parts of the country, as for transmitting weather reports, news items, and so on. Where the printingis done in a single line on a tape, the platen carriage is replaced by a tape wheel and the platen shift mechanism is omitted. To facilitate the transmission of long messages on sheets line'by line, -as in commercial typewriters, each machine is provided with a continuousroll of paper, which moves with the platen cylinder oris otherwise advanced linefor line in agreement with the platen movements of the transmitting machine. If the receiving machine is not intended for manual operation but onlyrfor radio control, it needs no key board and may have the type-actuating levers completely hidden. It will therefore be understood that, when in the claims I refer to a receiving typewriter having keys, I'do not necessarilyV mean a machine capable of manual operation byA means of keys, but I include any printing device having operating members which are the equivalent of (or correspond to) the keycontrolled members of the transmitting machine.

I direct particular attention to the absencev of all synchronizing mechanismV in my.. radiodynamic system, wherebythe apparatus is greatly simplified and its operation rendered more certain and reliable. of separate signals from the broadcastingYY station to control the operation of a movable part in the receiving apparatus. Nor does the element of time enter intothe operation of my invention.V

I meanby this that the 'modulating impulses in my transmitting system depend entirely on frequency and not on characteristically timed groups of impulses for; the different keys, as heretofore employed in radio telegraph printers. If the modulating frequencies of circuits 22 are within the audio range, as they preferably are, it is possible to use an ordinary radio set 38 in the receiving apparatus, thus further reducing the cost of the equipment. In the basic aspect of my invention, the modulating frequency circuits 22 may be individually controlled by any suitable means, andthe tuned receiving circuits 41 may control or operate various kinds of practical devices, machines or objects, which may be separately located, like ships, airplanes, and so on. It is evident that the ntransmitting element 14 and the receiving element 37 in Fig. 1 may also be operatively connected by Wires for transmission of the electric impulses.

AlthouglrI have shown and described certain apparatus, I want it understood that my invention is not limited to the details set forth. Changes and modificationsmay be made without departing from the scope of the invention as defined in the appended claims.

I claim as my invention:

1. In an electric transmitting system, a type- Writer having a set of keys and a shiftable platen l carriage, means whereby the operation of any key automatically causes a single group of .electric impulses of a certain frequency to be transmitted, and means whereby the returnof said carriage to initial position also causes asingle group'of elec- I do not even require the useV tric impulses of predetermined frequency to be transmitted, said single groups of frequencies being different for each key and said carriage.

2. In printing mechanism adapted to be controlled at each operation by'a single group of 'electric impulses, a set of individually movable type bars, a corresponding plurality of circuits tuned to different frequencies and closed at all times, means for selectively energizing any one of said tuned circuits, and voperative connections between each tuned circuit and one of said bars, said operative connections including means whereby the energizing of a single circuit by a single group of impulses having the proper frequency causes the corresponding bar to ybe moved to printing position.'

3. In printing mechanism adapted to beV controlled at each operation by a single group of electric impulses,l a set of nindividually movable type bars, an electromagnetic device for actuating each bar to printing position, an electrically tuned circuit associatedgwith each device, said tuned circuits being adapted to operate at different frequencies, and means whereby the operation of a tuned circuit by a single group of Yimpulses energizes the associated device to actuate the correspondingwtype bar.-

4. In printing mechanism adapted to be controlled at each operation by a single group of electric impulses, a set of individually movable type bars, a corresponding plurality of circuits tuned to different frequencies and closed at allY times, means for selectively energizing any one 'off said tuned circuits, means for connecting said tuned circuits in parallel to the output of a transmitting system, and operativeY connections between each tuned circuit and one of said bars,v said operativeY connections including means whereby the energizing of a single circuit by a single'group of impulses having the proper frequency causes the corresponding bar to be moved to printing position.

5. In printing mechanism adapted to be controlled at each operation by a single group of electric impulses, a set of individually movable type bars, an electromagneticievice for actuating each bar to printing position, an electrically tuned circuit associated with each device, said tuned circuits being closed at all times and adapted to operate at different frequencies, means whereby the operation of a single tuned circuit by a single group of in'pulses energizes the associated device to actuate the corresponding type bar, and means for connecting saidY tuned circuits to the output of electric receiving apparatus for individual Ycontrol by the frequencies of the received impulses.

5. In a typewriter adapted to be operated by t for causing movement of the bar to printing posi-Y tion when its associated circuit is energized, and

means controlled by the energizing of thetuned circuit associated with said carriage for rotating the latter one space and returning it to initial position; A

'7. In printing mechanism adapted toY be controlled at each operation by asingle group of impulses, a set of individually movable type bars, an electromagnetic device for actuating each bar to printing position, each of said devices including a coil, means for connecting said coils in par- 'i5-c allel to a common source of current, a normally open switch in the circuit of each coil, a plurality of tuned circuits corresponding to the number of type bars and adapted to operate at different frequencies, each of said tuned circuits being closed at all times and including an electromagnet adapted when energized to close onev of said switches, whereby the energizing of a tuned circuit by a single group of impulses energizes the electromagnetic device of the type` bar corresponding to that circuit and moves the bar to printing position, and means for connecting said tuned circuits to the output of electric receiving apparatus for individual control by the frequencies of the received impulses.

8. In an electric typewriter system, the combination of a transmitting typewriter and a corresponding receiving typewriter, each typewriter having the usual keys and shiftable platen carriage, means for transmitting the operation of v any key in the transmitting machine to the corresponding key in the receiving machine, said transmitting means including a plurality of circuits of diierent frequencies individually controlled by the transmitting machine and a plurality of correspondingly tuned receiving circuitsr for controlling the operation of the receiving machine, said transmitting means also including leo means whereby the operation of any key causes only a single group of impulses to be transmitted, means in said receiving typewriter whereby a singley group of impulses generated by a single key is suicient to operate the corresponding receiving key, and means whereby the rotary and sliding movements of the platen in the transmitting machine are each communicated by a single group of impulses of a certain frequency to the platen of the receiving machine.

9. In an electric typewriter system, transmitting apparatus including a typewriter with a shift key to permit printing from the upper case of the type bars, means controlled by the operative movement of the shift key for generating electric impulses of a certain frequency, means controlled by the return movement of the shift key for generating electric impulses of a diiferent frequency,

vin combination with receiving apparatus including a typewriter with a shift lever, an electromagnetic device for operating said lever, means for automatically locking said lever in actuated position, means whereby the irst set of said transonly the other switch by the return movement of -v said key, and an operative circuit controlled by each switch. Y

11. In an electric remote-control system, al

member adapted to be actuated in opposite directions, stop means for limiting the movement of said member in either direction, means for normallyholding said member against one of said stop means, means for lclosing an electric crcuit of a certain frequencyy by the movement of said member in one direction, means for closing a second electric circuit of a different frequency by the movement of said member in the other and a remotely located receiving typewriter, each typewriter having a set of movable type bars and a shiftable platen, a hand-operable member in p the transmitting machine for rotating the platen to the next vprinting line and returning it to initial position, means whereby the operation of said membercloses an electric circuit of a certain frequency, and means controlled by said single group of impulses for automatically duplicating said two movements of the transmitting platen inthe platen of the receiving machine, whereby the message typed by the latter is a line-for-line duplicate of the message typed on the platen of the transmitting machine.

13. In an electric remote-control printing system, the combination of a transmitting typewriter and a remotely located receiving typewriter, eacli typewriter having individually operable type bars and a shiftable platen, electric connections between said typewriters whereby the actuation of any type bar in the transmitting machine automatically operates the corresponding type bar in the receiving machine, said electric lconnections including means whereby the operation of any type bar closes an electric circuit of a certain frequency which is different for each type bar, and electric means controlled by the longitudinal and rotary movements of the platen in the transmitting machine for automatically duplicating said movements in the platen of the receiving machine, whereby the received message l and a remotely located receiving typewriter, each typewriter having double-case type bars and a platen shiftable relatively to the type for printing from the upper and lower case, electric connections between said typewriters whereby the actuation of any type bar in the transmitting machine automatically operates the corresponding type bar in the receiving machine, said-electric connections including means whereby the operation of any type bar and the shifting of said platen closes an electric circuit of'a certain frequency which is different for each type bar and for said platen, and electrically controlled means whereby the, relative shifting of Aplaten and type bars in the transmitting machine to print from either case automatically produces a similar relative g shifting of platen and type bars inV the receiying machine for printing from. the same case, said electrically controlled means including a coil in the receiving machine adapted to bel energized only by electric impulses of a frequency different from al1 the aforesaid frequencies generated by the operation of the type bars.

15. In a remote-control printing system, transmitting apparatus comprising a typewriter, a plurality of electric circuits for generating impulses of different' frequencies, a normally open switch in each circuit for individual control of these circuits, there being a switch for each typewriter key, means whereby the operation of a key closes only its associated switch to generate a single loC group of impulses of a certain frequency, a common output circuit for all the groups of impulses controlled by said keys, in combination with receiving apparatus comprising a typewriter having individually movable type bars, a differently tuned circuit for each type bar of the receiving typewriter, said tuned receiving circuits being closed at all times and corresponding to said tuned transmitting circuits, means whereby they single group of impulses produced by the closing of a tuned transmitting circuit energizes the correspondingly tuned receiving circuit, and means whereby the energizing of a. tuned receiving circuit actuates the associated type bar.

16. In a remote-control printing system, a transmitting typewriter having a shiftable carriage and a rotary platen mounted thereon, a hand-operable lever pivotally mounted on said carriage and operatively connected with said platen for rotating the latter, said lever also forming a handle for shiftingthe carriage, and a normally open switch automatically closed by said lever during its pivotal movement to rotate the platen, said switch being held closed during the shifting of the carriage to initial position by said lever.

1'7. In a remote-control printing system, a transmitting typewriter having a shiftable carriage and a rotary platen mounted thereon, an operating member movably mounted on said carriage for shifting the latter to initial position and also for rotating the platen to the next printing line, means controlled by the movement of said member relatively to said carriage for energizing an electric circuit, a receiving typewriter also having a shiftable carriage and a rotary platen mounted thereon, and means controlled by said energized circuit for transmitting the carriage and platen movements of the sending machine to the receiving machine.

18. In a remote-control printing system, a receiving typewriter having a shiftable. carriage on which a platen is rotatably mounted, an electromagnet adapted to be energized for rotating said platen to the next printing line, a normally open switch, means controlled by the operation of said electromagnet for closing said switch, and electric mechanism controlled by said closed switch for shifting said carriage to initial position.

19. In a remote-control printing system, a receiving typewriter having a shiftable carriage on which a platen is rotatably mounted, an electric motor adapted toV be connected with said carriage for shifting the same toI initial position, means for normally maintaining an inoperative relationship between said motor and said carriage, an electromagnet adapted to be energized for rotating said platen to the next printing line, and means automatically controlled by the operation of said electromagnet for establishing an operative relationship between said motor and said carriage, whereby the latter is shifted to initial position for the next printing line. A

20. In an electric control system, a member movable in alternately opposite directions from normal position to a dei'lnite operative position and back to initial position, an electric circuit of certain frequency automatically closed by the movement of said member from normal to operative position, another circuit of a different frequency automatically closed by the return movement of the operated member to normal position, and means for utilizingeach set of frequencies.

21. The combination of a pair of typewriters located remotely from each other, each typewriter having the usual platen rotatable for line spacing, means whereby rotation of the platen in one machine automatically closes an electric circuit of a certain frequency, and electromagnetic means controlled by said electric impulses for imparting a corresponding rotation to the platen of the other machine.

22. An electric transmitting system comprising a set of manually operable printing keys, and means whereby the operation of any key automatically causes a single group of electric impulses of a certain frequency to be impressed upon the output circuit of said system, each group of impressed frequencies being different for each key, in combination with a receiving system having recording members corresponding to said keys, and means in said receiving system whereby the group of impulses transmitted by an actuated key operates the corresponding member to record the transmitted character or symbol, said last-mentioned means including a plurality of differently tuned circuits operatively connected with the output circuit of said transmitting sys` tem, each tuned circuit being closed at all times and energized by only one group of transmitted impulses.

23. An electric transmitting system having a set of manually operable printing keys, and means whereby the operation of 'any key causes a single group of `electric impulses of a certain frequency to be impressed upon the output circuit of said system, each group of frequencies being different for each key, in combination with a receiving system having a pair of main input leads operativelyA connected with the output circuit of said transmitting system, a plurality of differently tuned circuits connected in parallel to said input leads and closed at all times, each tuned circuit containing an electromagnetic coil adapted to be energized by the operation of one of said keys, a plurality of recording members corresponding to said keys and coils, and means whereby the energizing of any one of said coils causes operation@l of the corresponding member to record the transmitted character or symbol. 24. An electric transmitting station having a printing machine provided with a plurality of manually operable type members, means whereby the operation of each member causes a single group of electric impulses of predetermined frequency to be transmitted, said frequencies being different for each type member, in combination with an electric receiving station operatively connected with said transmitting station and having a similar printing machine provided with individually operable type members, and means controlled bythe frequency of a single group of transmitted impulses for operating a type member in the receiving machine corresponding to the type member which caused transmission of said group of impulses, said last-mentioned means including a plurality of electromagnetic coils connected each to an electrically tuned circuit adapted to be energized by only one group' of transmitted impulses, each of said tuned 4circuits being electrically responsive to a different frequency.

25. In printing mechanism adapted to be controlled at each operation by a single group of electric impulses, a plurality of individually operable printing members, a corresponding plurality of circuits electrically tuned to different frequencies, means for selectively energizing any onel of said electrically tuned circuits, and means whereby the energizing of a tuned circuit by a single group of impulses automatically operates the corresponding printing member.

26. In printing mechanism adapted to be con.

trolled at each operation by a single group of electric impulses, a plurality of individually operable printing members, a corresponding plurality of circuits electrically tuned to diierent frequencies, a. common input coil to which all of said tuned circuits are connected for individual operation, selective means for impressing upon said coil a group of electricimpulses of a certain frequency to energize the correspondingly tuned circuit, and means whereby the energizing of a tuned circuit by a single group of impulses automatically operates the corresponding printing l member.

27. An electric transmitting system comprising a set of manually operable printing keys, and means whereby the operation of any key automatically causes a single group of electric impulses of a certain frequency to be impressed upon the output circuit of said system, each group of impressed frequencies being' diierent for each key, in combination with a receiving system having recording members corresponding to said keys, and means in said receiving system whereby the group of impulses transmitted by an actuated key operates the corresponding member to record the transmitted character or symbol, said lasthaving a rotary and shiftable platen, means con- 29. n a remote-control printing system, a typewriter having a rotary and shiftable platen, means for automatically energizing an electric circuit of a certain frequency in response to the rotary movement of the platen," and means for automatically energizing another circuit of a different frequency in response to the shifting of said platen .to initial position.

30. In a remotely controlled printing machine trolled by electric impulses of a certain frequency for rotating said platen, and means controlled by electric impulses of a different frequency for shifting the platen to initial position.

31. In an'electric remote-control printing system, the combination of a transmitting typewriter and a remotely located receiving typewriter, each typewriter having a set of movable typebars and a platen which is rotatable and shiftable to initial position, mechanism associated with the transmitting machine whereby each operation thereof transmits to the receiving machine a single group of electric impulses of a certain frequency which is different for each key and for each of said twof platen movements, and mechanism associated with the receiving machine and adapted to be operated by each group of trans mitted impulses for duplicating each operation of thev transmitting machine, whereby the matter typed on the transmitting machine is automatically reproduced line. for line on the receiving machine.

32. In a remotely controlled printing machine having a rotary platen,- means controlled by electric impulses of a' certain frequency for rotating 110 said platen from one line position to the next.

Anomri A. THOMAS. 

